Injection mold friction puller

ABSTRACT

A friction puller for an injection mold is disclosed. The friction puller has a bolt with a head portion and a threaded portion. The friction puller has first and/or second first substantially hemispherical wedges having a first and/or second passages running through them for the bolt and allow lateral float about the bolt. The friction puller also has a deformable jacket having a third passage running through is for the bolt and first and second substantially hemispherical cups for receiving the first and second substantially hemispherical wedges. The first hemispherical wedge can have a vent relief notch disposed in a top surface of the first hemispherical wedge. The deformable jacket can have a jacket vent notch disposed in a top surface of the deformable jacket. The bolt head and the jacket can have alignment indicator marks thereon. The bolt threads can have a variable pitch diameter.

CROSS REFERENCE TO RELATED APPLICATION

This Patent Application is a continuation-in-part patent application ofU.S. patent application Ser. No. 12/107,060, filed on 21 Apr. 2008,which is the co-pending parent application and which is incorporated byreference herein and is made a part hereof, including but not limited tothose portions which specifically appear in this Patent Application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to injection molding devices, and morespecifically to a friction puller of a multiple plate injection mold.

2. Discussion of Related Art

Friction pullers are used in injection mold application to help controlthe sequential movements of various plates during mold operations. Onesuch friction puller is shown in German Patent No. DE 2815698, which isassigned to the HASCO Company. Friction pullers made according HASCOhave a bolt which has a substantially conical shaped shank. The bolt isinserted into a resin jacket that has a corresponding substantiallyconical shaped passage for receiving the bolt shank. When the bolt istightened, the bolt head compresses the jacket lengthwise and the shankpresses laterally on the jacket. The result is that under the load fromthe tightened bolt, the jacket has an increased diameter compared towhen it is in an unloaded condition.

Another type of friction puller is also produced by HASCO. In thesefriction pullers, a bolt with a straight set of threads is used. Thebolt is secured into a key member that passes through one of the moldplates. The key has at least one flat surface to prevent the key fromrotating inside the mold plate. The end of the key that receives thatbolt has a hemispherical wedge section integral to or fixed to the keymember. A resin jacket is again used. The jacket has a hemispherical cupinside one end of the jacket to correspond to the hemispherical wedge onthe key member. The other end of the jacket has a second hemisphericalcup for receiving a hemispherical washer used between the bolt head andthe jacket. Again, when the bolt is tightened, the hemispherical washerand hemispherical wedge compress the jacket lengthwise forcing thejacket to increase slightly in diameter.

A problem encountered with both of these types of friction pullers isthat they do not accommodate typical manufacturing conditions withrespect to installation or operational environments, which results ininconsistent performance. For example, these products are fix mountedinto the mold plates. Thermal expansion, build tolerances and the likecan lead to the pullers not being centered with respect to therespective pockets in the opposing mold plates. While small, thesemisalignments can cause the mold to lock because of different forcelevels exerted by each of the friction pullers in the mold. Typically,multiple friction pullers are used in a single mold.

Another problem encountered with both of the types of friction pullersdescribed above is the creation of air pressure differentials duringuse. As the pullers are designed to friction fit into the pockets thatreceive them, often the puller creates an air tight seal against thepocket. During mold close, the mold has to compress the air in thepocket to close the mold. This compressed air wants to push the pullerout of the pocket. Alternatively, if the air escapes-the pocket duringmold closure, but the jacket creates an air tight seal once the mold isfully closed, a vacuum is created in the pocket when the puller attemptsto pull out from the pocket. Neither of the friction pullers describedabove provide for air to flow in and out of the pocket during mold openan mold closure operations. Accordingly, either the compressed air orvacuum conditions can occur randomly, creating an undesirable variationin the force exerted by the friction pullers.

Thus, there remains a need for an improved friction puller. Thereremains a need for a self-aligning friction puller. There remains a needfor a friction puller to controllably allow air to pass into and out ofthe pocket that receives the friction puller.

SUMMARY OF THE INVENTION

In view of the deficiencies described above, it is an object of thepresent invention to provide an improved friction puller.

It is a further object of the present invention to provide a frictionpuller that is self-aligning.

It is a further object of the present invention to provide a frictionpuller that controllably allows air to pass into and out of the pocketthat receives the friction puller.

The present invention is a friction puller for an injection mold. Thefriction puller has a bolt, the bolt has a head portion and a threadedportion. The friction puller also has a first substantiallyhemispherical wedge. The first substantially hemispherical wedge has afirst passage running through it for the bolt. The first passage allowsthe first substantially hemispherical wedge a first predetermined amountof lateral float relative to the bolt. In some embodiments of thepresent invention, the friction puller has only one substantiallyhemispherical wedge. In other embodiments according to the presentinvention, the friction puller also has a second substantiallyhemispherical wedge. The second substantially hemispherical wedge has asecond passage running through it for the bolt. The second passageallows the second substantially hemispherical wedge a secondpredetermined amount of lateral float relative to the bolt.

The friction puller also has a deformable jacket. The jacket has a thirdpassage running through it for the bolt. In some embodiments of thepresent invention, the jacket has only a first substantiallyhemispherical cup for receiving the one substantially hemisphericalwedge. In other embodiments according to the present invention, thejacket has a first substantially hemispherical cup for receiving thefirst substantially hemispherical wedge and a second substantiallyhemispherical cup for receiving the second substantially hemisphericalwedge.

Preferably, the first hemispherical wedge has a least one vent reliefnotch disposed in a top surface of the first hemispherical wedge. Thevent relief notch allows air to pass through during mold operation.Likewise the deformable jacket preferably has at least one jacket ventnotch disposed in a top surface of the deformable jacket. The jacketvent notch also allows air to pass through during mold operation.

Preferably, the head portion of the bolt has at least one bolt alignmentindicator mark in it. Likewise, the deformable jacket has at least onejacket alignment indicator mark on it.

Preferably, the threads on the threaded portion of the bolt have avariable pitch diameter.

In a typical three-plate injection molding machine, as the name implies,there are three plates involved in the molding operation. Typicallythese plates are referred to as the X plate, the B plate, and the Aplate. A mold pattern is formed between a portion of the B plate and theA plate. A runner pattern is formed on the A plate which faces the Xplate. The B plate is bolted to a support plate. The support plate isfurther secured to an ejector box or housing. The ejector box is clampedto a movable platen of the molding machine. The X plate is bolted to atop clamp plate, usually with two or more shoulder bolts. The top clampplate is fixed to the opposing platen of the injection molding machine.

During the molding operation, the mold and runner patterns are filledwith heated plastic injected from a reservoir connected to the top clampplate. When the plastic has cooled, the moving platen pulls the ejectorbox and the associated support plate and B plate away from the A plate,thus initiating the sequential opening of the mold plates and theeventual removal of the molded parts and runner.

As the mold opens, the B plate and associated support plate are pulledaway. At least one friction puller is secured to the B plate. Thedeformable jacket of the friction puller engages, via an interferencefit, with a pocket in the A plate. The friction puller holds the A plateand the B plate together as the mold clamping force is removed. Springsbetween the A plate and the X plate begin to expand and separate the Aplate and X plate at a first parting line. The runner breaks free fromthe A plate and remains attached to the sucker pins. Sucker pins arepins secured to the top plate and pass through an opening in the Xplate. The sucker pins serve to hold the runner in place while the Aplate, B plate, and the support plate are moved away from the X plate.Further movement of the X plate away from the top clamp plate causes therunner to be stripped from the sucker pins.

When the shoulder bolts reach the end of their travel, the shoulderbolts hold the A plate in position and the B plate is moved furtheraway. The A plate and the B plate separate at a second parting line.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from thefollowing detailed description taken in conjunction with the followingfigures, wherein like reference numerals represent like features.

FIG. 1 shows an exploded front view of a friction puller according toone embodiment of the present invention.

FIG. 1A shows a close up front view of the bolt threads of a frictionpuller according to the present invention.

FIG. 1B shows an exploded front view of a friction puller according toanother embodiment of the present invention.

FIG. 2 shows an exploded perspective view of a friction puller accordingto one embodiment of the present invention.

FIG. 2A shows an exploded perspective view of a friction pulleraccording to another embodiment of the present invention.

FIG. 3 shows an assembled perspective view of a friction pulleraccording to the present invention.

FIG. 4 shows a top view of a friction puller according to the presentinvention.

FIGS. 5A-5C show a three plate mold having a friction puller accordingto the present invention installed therein going through an openingsequence.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiments in many differentforms, there are shown in the drawings and will herein be described indetail, preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

The present invention is a friction puller 100 for an injection mold.FIG. 1 shows an exploded front view of a friction puller according tothe present invention. FIG. 2 and FIG. 2A each shows an explodedperspective view of a friction puller, each according to a differentembodiment of the present invention. FIG. 3 shows an assembledperspective view of a friction puller according to the presentinvention. The friction puller 100 has a bolt 110, and the bolt 110 hasa head portion 105 and a threaded portion 120.

The friction puller 100 also has a first substantially hemisphericalwedge 130. The first substantially hemispherical wedge 130 has a firstpassage 150 running through it for the bolt 110. The first passage 150allows the first substantially hemispherical wedge 130 a firstpredetermined amount of lateral float relative to the bolt 110. That is,the diameter of the first passage 150 is larger than the diameter of thethreaded portion 120 of the bolt 110. In various preferred embodiments,the first substantially hemispherical wedge 130 has about 0.010 inchesof lateral float. This allows the friction puller 100 to self-align, orself-center itself during use. Additionally, this allows for thermalexpansion differences between the mold plates.

In some embodiments according to the present invention, such as shown inFIG. 1B and FIG. 2A, the friction puller 100 has only one substantiallyhemispherical wedge 130. The only one substantially hemispherical wedge130 can be in a position such as shown in FIG. 1B and FIG. 2A, or can bepositioned at an opposite end of a deformable jacket 160. In otherembodiments according to the present invention, the friction puller 100also has a second substantially hemispherical wedge 210, such as shownin FIGS. 1 and 2. The second substantially hemispherical wedge 210 has asecond passage 220 running through it for or to accommodate the bolt110. The second passage 220 allows the second substantiallyhemispherical wedge 210 a second predetermined amount of lateral floatrelative to the bolt 110. In various preferred embodiments, the secondsubstantially hemispherical wedge 210 has about 0.010 inches of lateralfloat. This allows the friction puller 100 to self-align, or self-centeritself during use. Additionally, this allows for thermal expansiondifferences between the mold plates.

The friction puller 100 also has the deformable jacket 160. The jacket160 has a third passage 190 running through it for or to accommodate thebolt 110. The jacket 160 has a first substantially hemispherical cup 180for receiving the first substantially hemispherical wedge 150 and asecond substantially hemispherical cup 200 for receiving the secondsubstantially hemispherical wedge 210. The jacket 160 preferablyincludes a step in outer diameter, as can be seen in FIG. 1. The step inouter diameter further enables lateral float of the jacket 160.

Preferably, the first hemispherical wedge 130 has a least one ventrelief notch 140 disposed in a top surface of the first hemisphericalwedge 130. The vent relief notch 140 allows air pass through or by thefirst hemispherical wedge 130 during mold operation. Likewise thedeformable jacket 160 preferably has at least one jacket vent notch 170disposed in a top surface of the deformable jacket 160. The jacket ventnotch 170 also allows air to pass through or by deformable jacket 160during mold operation. By allowing air to pass through or by eachnecessary element during mold operation, the adverse compressed air andvacuum conditions described above are avoided.

Preferably, the head portion 105 of the bolt 110 has at least one boltalignment indicator mark 250 in it or on a corresponding surface.Likewise, the deformable jacket 160 has at least one jacket alignmentindicator mark 260 on it or on a corresponding surface. The alignmentindicator marks 250 and 260 allow the mold engineer and mold builder tosee, and hopefully record, how many turns or rotations of the bolt 110,such as relative to the deformable jacket 160, have been made duringinstallation or maintenance of the mold. For example, each bolt 110could be turned or rotated the same number of revolutions to achieve thesame friction force. Additionally, any adjustments made to the bolt,e.g., a fraction of a turn, could also be seen and recorded. In variouspreferred embodiments, the bolt alignment indicator mark 250 is an arrowor other similar mark or structure disposed on a top surface of the headportion 105 of the bolt 110 and the jacket alignment indicator mark 260comprises an arrow or other similar mark or structure disposed on a topsurface of the deformable jacket 160. Any suitable number of alignmentmarks 250 and 260 can be used. In various preferred embodiments, thereare four jacket alignment indicator mark comprises 260.

FIG. 1A shows a close up front view of the bolt threads of a frictionpuller 100 according to the present invention. Preferably, the threadson the threaded portion 120 of the bolt 110 have a variable pitchdiameter. That is, the threaded portion 120 of the bolt 110 has a firstpitch diameter at a first section 125 of the threaded portion 120 and asecond pitch diameter at a second section 127 of the threaded portion120. The first pitch diameter can be different from the second pitchdiameter.

This variable pitch diameter is different from other fasteners.Typically a fastener is engineered to stretch when the fastener head islimited from travel. The stretching is what creates the tighteningtorque. Although the bolt 110 of the present invention resembles atypical fastener installation, the bolt head 105 is never mating to asolid that limits its travel and produces the tightening torque. Thevariable pitch diameter resists unintentional rotational movement orbacking out of the bolt 110 during operation. Furthermore, when the bolt110 is unscrewed a specified amount for mold maintenance or otherreasons the bolt 110 will hold its position without any force beingexerted on it from the jacket 160.

FIGS. 5A-5C show a three plate mold having a friction puller accordingto the present invention installed therein going through an openingsequence. In a typical three-plate injection molding machine, as thename implies, there are three plates involved in the molding operation.Typically these plates are referred to as the X plate 310, the B plate320, and the A plate 330. A mold pattern 370 is formed between a portionof the B plate 320 and the A plate 330. A runner pattern 335 is formedon the A plate 330 which faces the X plate 310. The B plate 320 isbolted to a support plate 350. The support plate 350 is further securedto an ejector box or housing (not shown). The ejector box is clamped toa movable platen of the molding machine. The X plate 310 is bolted to atop clamp plate 360, usually with two or more shoulder bolts 345. Thetop clamp plate 360 is fixed to the opposing platen of the injectionmolding machine. FIG. 5A shows the mold in a closed position.

During the molding operation, the mold 370 and runner patterns 335 arefilled with heated plastic injected from a reservoir 380 connected tothe top clamp plate. When the plastic has cooled, the moving platenpulls the ejector box and the associated support plate 350 and B plate320 away from the A plate 330, thus initiating the sequential opening ofthe mold plates and the eventual removal of the molded parts and runner340.

As the mold opens, the B plate 320 and associated support plate 350 arepulled away, shown in FIG. 5B. At least one friction puller 100,corresponding to any one of the different embodiments according to thepresent invention, is secured to the B plate 320. The deformable jacket160 of the friction puller 100 engages, via an interference fit, apocket 325 in the A plate 330. The friction puller 100 holds the A plate330 and the B plate together as the mold clamping force is removed.Springs between the A plate 330 and the X plate 310 begin to expand andseparate the A plate 330 and X plate 310 at a first parting line. Therunner 340 breaks free from the A plate 330 and remains attached to thesucker pins 390. Sucker pins 390 are pins secured to the top plate 360and pass through an opening in the X plate 310. The sucker pins 390serve to hold the runner 340 in place while the A plate 330, B plate320, and the support plate 350 are moved away from the X plate 310.Further movement of the X plate 310 away from the top clamp plate 360causes the runner 340 to be stripped from the sucker pins 390.

When the shoulder bolts 345 reach the end of their travel, shown in FIG.5C, the shoulder bolts 345 hold the A plate 330 in position and the Bplate 320 is moved further away. The A plate 330 and the B plate 320separate at a second parting line.

While specific embodiments have been illustrated and described, numerousmodifications come to mind without significantly departing from thespirit of the invention and the scope of protection is limited by thescope of the accompanying claims. These modification include, but arenot limited to, replacing other types of friction pullers with frictionpullers made according to the present invention and or retrofittingother types of friction pullers using the principles of the presentinvention.

1. A friction puller for an injection mold comprising: a substantiallyhemispherical wedge forming a first passage therethrough, a deformablejacket having a second passage therethrough and forming a substantiallyhemispherical cup for receiving said substantially hemispherical wedge,and said substantially hemispherical wedge and/or said deformable jackethaving a vent.
 2. The friction puller according to claim 1, furthercomprising a bolt having a head portion, said head portion having atleast one bolt alignment indicator, and said deformable jacket having atleast one jacket alignment indicator mark.
 3. The friction pulleraccording to claim 2, wherein said at least one bolt alignment indicatorcan be turned relative to said at least one jacket alignment indicatormark.
 4. The friction puller according to claim 1, further comprising abolt, said first passage for said bolt, and said first passage allowingsaid substantially hemispherical wedge a predetermined amount of lateralfloat relative to said bolt.
 5. The friction puller according to claim1, further comprising a bolt having a threaded portion, said firstpassage for said bolt, and said bolt having a first pitch diameter at afirst section of said threaded portion and a second pitch diameter at asecond section of said threaded portion.
 6. A friction-puller for aninjection mold comprising: a bolt having a head portion, a deformablejacket having a passage therethrough for said bolt, said head portionhaving at least one bolt alignment indicator, said deformable jackethaving at least one jacket alignment indicator mark, and said at leastone bolt alignment indicator turnable relative to said at least onejacket alignment indicator mark.
 7. The friction puller according toclaim 6, further comprising a substantially hemispherical wedge forminga second passage therethrough, said passage of said deformable jacketforming a substantially hemispherical cup for receiving saidsubstantially hemispherical wedge, and said substantially hemisphericalwedge and/or said deformable jacket having a vent.
 8. The frictionpuller according to claim 6, wherein said bolt has a threaded portion,said first passage is for said bolt, and said bolt has a first pitchdiameter at a first section of said threaded portion and a second pitchdiameter at a second section of said threaded portion.
 9. A frictionpuller for an injection mold comprising: a bolt having a threadedportion, a deformable jacket having a passage therethrough for saidbolt, and said bolt having a first pitch diameter at a first section ofsaid threaded portion and a second pitch diameter. at a second sectionof said threaded portion.
 10. The friction puller according to claim 9,wherein said head portion has at least one bolt alignment indicator,said deformable jacket has at least one jacket alignment indicator mark,and said at least one bolt alignment indicator can be turned relative tosaid at least one jacket alignment indicator mark.
 11. The frictionpuller according to claim 9, further comprising a substantiallyhemispherical wedge forming a second passage therethrough, said passageof said deformable jacket forming a substantially hemispherical cup forreceiving said substantially hemispherical wedge, and said substantiallyhemispherical wedge and/or said deformable jacket having a vent.
 12. Afriction puller for an injection mold comprising: a bolt, said bolthaving a head portion and a threaded portion; a first substantiallyhemispherical wedge, said first substantially hemispherical wedge havinga first passage therethrough for said bolt, said first passage allowingsaid first substantially hemispherical wedge a first predeterminedamount of lateral float relative to said bolt; a second substantiallyhemispherical wedge, said second substantially hemispherical wedgehaving a second passage therethrough for said bolt, said second passageallowing said second substantially hemispherical wedge a secondpredetermined amount of lateral float relative to said bolt; and adeformable jacket, said jacket having a third passage therethrough forsaid bolt, a first substantially hemispherical cup for receiving saidfirst substantially hemispherical wedge, and a second substantiallyhemispherical cup for receiving said second substantially hemisphericalwedge.
 13. The friction puller according to claim 12, wherein said firsthemispherical wedge further has a least one vent relief notch disposedin a top surface of said first hemispherical wedge, said deformablejacket has at least one jacket vent notch disposed in a top surface ofsaid deformable jacket, and wherein said at least one vent relief notchand said at least one jacket vent notch permit air to pass through. 14.The friction puller according to claim 12, wherein said head portion ofsaid bolt has at least one bolt alignment indicator mark disposedthereon, and said deformable jacket has at least one jacket alignmentindicator mark disposed thereon.
 15. The friction puller according toclaim 14, wherein said bolt alignment indicator mark comprises an arrowdisposed on a top surface of said head portion of said bolt.
 16. Thefriction puller according to claim 14, wherein said jacket alignmentindicator mark comprises an arrow disposed on a top surface of saiddeformable jacket.
 17. The friction puller according to claim 16,wherein said at least one jacket alignment indicator mark comprises fouralignment indicator marks.
 18. The friction puller according to claim12, wherein said threaded portion of said bolt has a first pitchdiameter at a first section of said threaded portion and a second pitchdiameter at a second section of said threaded portion.
 19. The frictionpuller according to claim 12, wherein said first predetermined amount oflateral float relative to said bolt is about 0.010 inches.
 20. Thefriction puller according to claim 12, wherein said second predeterminedamount of lateral float relative to said bolt is about 0.010 inches. 21.The friction puller according to claim 12, further comprising aninjection mold comprising: at least an A plate, and a B plate; said Aplate having a pocket formed therein for receiving the friction puller;said B plate having the friction puller mounted thereon; and saiddeformable jacket and said pocket cooperatively engaging via aninterference fit between said deformable jacket and said pocket.
 22. Theinjection mold according to claim 21, wherein said interference fitbetween said deformable jacket and said pocket is about 0.002 inches.